Kenichi Mishima1, Nobuaki Egashira1, Nobue Hirosawa1, Megumi Fujii1, Yoshiaki Matsumoto2, Katsunori Iwasaki1 and Michihiro Fujiwara1,*
1Department of Physiology and Pharmacology, Faculty of Pharmaceutical Sciences, Fukuoka University, Fukuoka 814-0180, Japan
2Department of Pharmacology, School Nurse Training, Kyushu Women’s Jr. College, Kitakyushu 807-8586, Japan
*Corresponding author. FAX: +81-92-863-0389, E-mail: mfuji@fukuoka-u.ac.jp
Abstract: We investigated the characteristics of D9-tetrahydrocannabinol (THC)-induced impairment of learning and memory using an 8-arm radial maze task, a water maze, a visual discrimination task with 2 figures and a passive avoidance test in rats. THC (6 mg/kg, i.p.) impaired spatial memory in the standard task of the 8-arm radial maze. THC (4-6 mg/kg, i.p.) selectively impaired working memory in a reference and working memory task of the 8-arm radial maze. Even at a dose of 10 mg/kg, THC did not impair spatial memory in the water maze. In addition, THC at a dose of 6 mg/kg, which had inhibitory effects in the 8-arm radial maze, did not affect performance in the visual discrimination task. These results indicate that at low doses (2-6 mg/kg), THC may not produce visual function abnormalities. THC impaired retrieval (6 mg/kg, i.p.) as well as acquisition (10 mg/kg, i.p.) in the passive avoidance test. The consolidation process was also impaired by i.c.v. injection (100 mg), but not i.p. injection (6-10 mg/kg) of THC. These results suggest that THC-induced impairment of spatial memory is based on the selective impairment of working memory through its effects on acquisition and retrieval processes.
Keywords: 8-Arm radial maze, D9-Tetrahydrocannabinol, Passive avoidance, Water maze, Working memory
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